Although not specifically shown, a conventional spring assembly of this kind is constructed such that it includes a compression coil spring, a pair of sheets abutting respectively against opposite end portions of the compression coil spring, a pair of loop-like wires for imparting precompression to the compression coil spring, a pair of bushes having opposite ends of the respective loop-like wires fixedly embedded therein and fitted respectively in holes in the respective sheets, and a plate mounted on one of the sheets so as to center the bush associated therewith (see, for example, Patent Document 1).
When this spring assembly is actually to be assembled, one loop-like wire and the other loop-like wire are combined together in an intersecting manner, and then the opposite ends of each loop-like wire are fixedly embedded in the corresponding bush, and each bush is fitted into the hole in the sheet. As a result, the distance between the pair of sheets is regulated, and the compression coil spring is held in a shortened condition smaller a predetermined amount than its free length.
Patent Document 1: Japanese Patent No. 3,497,063